Jetting issue

[Deezy804]

Hey fellas I have a 03 rm 250 that I just got bored .060 ovr and port and polished vforce reeds and full procircuit pipes, I use the bike for drag. I removed the air box and ran a pod filter, now while I have a stock carb I don't know what its specs are but my bike dies after 2nd gear it's nasty on the hole but falls flat on it's face. I'm running 32:1 110 octane.. how do I make it right on the top end I have the power it just seems to be off tuned because of the pod filter what do I do?

[zig06]

Even for what you've done I think that the 110 octane is too much, just for the fun of it I'd like to see how it ran with pump premium.  Yes, port and polish should increase the need for a higher octane fuel, but 110 still seems excessive. 

[Deezy804]

93 oct is too low is bogs badly 

[mlatour]

Is there any way to re-install the stock intake boot for a test run ?

 

In some cases pod filters can surely create turbulence, 

as an example, in a mini-sprint car team (inline 4 from a street bike) I helped out a long time ago,

their pro built and tuned (on the dyno) engine fell flat on top end once installed in the car and run

under actual racing conditions,

until the pods were replaced by a proper enclosed airbox with individual velocity stacks to each carburetor.

[Deezy804]

10 hours ago, mlatour said:

Is there any way to re-install the stock intake boot for a test run ?

 

In some cases pod filters can surely create turbulence, 

as an example, in a mini-sprint car team (inline 4 from a street bike) I helped out a long time ago,

their pro built and tuned (on the dyno) engine fell flat on top end once installed in the car and run

under actual racing conditions,

until the pods were replaced by a proper enclosed airbox with individual velocity stacks to each carburetor.

It works pretty good with the air box but I need to get it tuned for the pod cause I drag race the bike and I've began taking extra weight off but again it runs decent but I want to let it breath a little bit more and with the pod the throttle response is crisp and very responsive 

[kxrob]

On 21/05/2017 at 10:10 AM, Deezy804 said:

Hey fellas I have a 03 rm 250 that I just got bored .060 ovr and port and polished vforce reeds and full procircuit pipes, I use the bike for drag. I removed the air box and ran a pod filter, now while I have a stock carb I don't know what its specs are but my bike dies after 2nd gear it's nasty on the hole but falls flat on it's face. I'm running 32:1 110 octane.. how do I make it right on the top end I have the power it just seems to be off tuned because of the pod filter what do I do?

I would say with the pod you are getting more air up top so you need a richer main to compensate 

you got any pics of the bike

[Deezy804]

if I'm correct I'd need a bigger main jet. Stock comes with a 175 main so I think I'll try a few to find that good spot 

[zig06]

Bingo.  If it runs better with the stock air box (reduces the low end bog compared to without) then that's just a lean issue on the pilot / air screw, so go up on the pilot if your air screw is more than 2 turns out.  And you only need higher octane if it's knocking ~ not bogging.  Excessive bogging could be caused by too much octane.

Finally, pod filters really do not perform better than most air boxes, air boxes help to channel and straighten the air as it goes into the carb.  Do you at least have a plate or guard of some kind to prevent the paddle tire from tossing pounds of dirt into the filter?

My advise:  Back off the octane and put the stock air box back on and jet your bike to run right like that.  Your engine really isn't that far off a stock bike.

[GlennRay]

15 minutes ago, zig06 said:

Bingo.  If it runs better with the stock air box (reduces the low end bog compared to without) then that's just a lean issue on the pilot / air screw, so go up on the pilot if your air screw is more than 2 turns out.  And you only need higher octane if it's knocking ~ not bogging.  Excessive bogging could be caused by too much octane.

Finally, pod filters really do not perform better than most air boxes, air boxes help to channel and straighten the air as it goes into the carb.  Do you at least have a plate or guard of some kind to prevent the paddle tire from tossing pounds of dirt into the filter?

My advise:  Back off the octane and put the stock air box back on and jet your bike to run right like that.  Your engine really isn't that far off a stock bike.

You are going to kill your engine shortly with a pod air filter in a sand drag environment.

[zig06]

3 minutes ago, GlennRay said:

You are going to kill your engine shortly with a pod air filter in a sand drag environment.

You are completely correct!

I wanted to say that, but I'm trying to be nice.  FYI:  The Michigan trails are mostly like riding in beach sand with trees, and there's no way on this earth that I'd ride ANY dirt bike (even a Honda "GASP") using a pod filter. 

[Deezy804]

It's all good fellas give it to me straight but every bike has a pod set up where I run/drag at and I'm not doing the monkey see monkey do role either and run like a bat outta hell and I've tried 93 oct vs 110 with the airbox (but with the pod it's way more responsive on the throttle) the 110 it runs perfect but it's not really answering my question I don't want to go back to the air box I want to tune the carb to the pod filter and it's racing if it blows I'll rebuild it just like I did this one not to be a smart ass but I want to tune it to the pod filter that's all.

Edited May 23, 2017 by Deezy804
Had more to say

[GlennRay]

11 minutes ago, zig06 said:

You are completely correct!

I wanted to say that, but I'm trying to be nice.  FYI:  The Michigan trails are mostly like riding in beach sand with trees, and there's no way on this earth that I'd ride ANY dirt bike (even a Honda "GASP") using a pod filter. 

I wouldn't ride a street bike in Arizona with pod air filters.  They just don't filter well and these days the stock air-filtration systems work so good you would be crazy to not use them.

[GlennRay]

Welll, its your engine and your pocket book, so what is the bike doing that you don't like?  First off, what fuel/oil mixture are you running and what kind of oil?

 

[Deezy804]

24 minutes ago, GlennRay said:

Welll, its your engine and your pocket book, so what is the bike doing that you don't like?  First off, what fuel/oil mixture are you running and what kind of oil?

 

When the bike leaves from 1st and 2nd it's hauls ass but to 3rd and so on it's like the bike doesn't progress and I'm almost certain it's because of the switch from airbox to pod.. I'm running on 110octane 32:1 klotz stock carb and jetting 

[GlennRay]

I would try decreasing the fuel/oil mix to 50:1.  I am about to say something that will cause the forum to explode, but more oil in your gas makes the engine run lean.  Less combustible fuel is getting in there with each piston stroke because of the increased oil level.  You should be able to go to a 50:1 fuel/oil mix and not suffer any reliability consequences.  If you pulled the spark plug out of you bike right now, what would it look like?  Is it sooty black, dark chocolate brown, medium brown, tan, or light tan?  Look at this before you change your fuel oil mix and afterwards as well.  I would change the spark plug when you change the fuel/oil mix so that you can have one example of each to compare. 

[Deezy804]

I'll take that into consideration and I'll check the plug and see 

[GlennRay]

Just now, Deezy804 said:

I'll take that into consideration and I'll check the plug and see 

I'm not trying to dodge the jetting issue, I am just pointing out that other things can affect the way your bike runs.  It sounds like your bike is leaning out on the top end in the upper gears.  I would reduce the fuel/oil mixture first and see how that goes.

[Deezy804]

Man it's all good im accepting all opinions and I agree with u cause I ran out of oil one day and mixed it a little lighter and it did a little better I'll try 40:1 but 50:1 sounds a little too lean to me but I'll def try it. Thanks 

[GlennRay]

I ran my MX and Trials bikes at 64 to 1 and never had a problem, even here in blazing Arizona.  50:1 is not lean enough for you, but try that step first, or if that scares you 40:1.  I predict that 75:1 is going to be the right ratio for you.

[Deezy804]

I try a few ratios